SPOROZOA 429 



these measures has demonstrated the possibility of effectively 

 controlling this disease even in the tropics. 



Plasmodium Kochi. This is a malarial parasite which causes 

 a mild fever in monkeys. It is not transmissible to man. Other 

 species of malarial parasites have been recognized in these 

 animals. 



Babesia 1 Bigemina. Smith and Kilborne discovered this 

 organism in the red blood-corpuscles of cattle suffering from 

 Texas fever. The parasite is pear-shaped, 2 to 4/x long and 1.5 to 

 2/x wide and usually occurs in pairs within the erythrocytes. The 



J I * / * 



,/ 



'* 



FIG. 205. Babesia bigemina. Characteristic forms in the peripheral blood of cattle. 

 X2000. (After Doflein.) 



cytoplasm is quite clear without granules or pigment and contains 

 one or two chromatin bodies. Minute ameboid forms are also 

 found. Multiplication apparently takes place by longitudinal 

 division of the pear-shaped forms as well as by multiple division 

 of the ameboid forms. Macrogametocytes and microgametocytes 

 have been recognized. The transmission of the parasite from 

 animal to animal is effected by the cattle tick, Boophilus boms, 

 (Rhipicephalus annulatus) as was conclusively demonstrated by 

 Smith and Kilborne, the first instance in which such a relation 



1 The generic name Pyrosoma bestowed by Smith and Kilborne in 1893 is incor- 

 rect, because this is the name of a genus of marine animals belonging to the Tuni- 

 cata. Babesia proposed by Starcovici in 1893 has the next claim to priority. 



